Letter of R. Isaac the Blind to the Kabbalists of Gerona (ca. 1235)

    For I was filled with great concern when I saw scholars, men of understanding and Hasidim, engaging in long discourses and presuming in their books and letters to write about great and sublime matters [of the Kabbalah]. But what is written cannot be kept in the closet; often, these things are lost or the owners die and the writings fall into the hands of fools or scoffers, and the name of heaven is thus profaned. And this is in fact what happened to them. As long as I was still with them, in this life, I often warned them against this tendency, but since I separated myself from them [since their death?], they have been the cause of much harm. I am of an entirely different habit, since my fathers were indeed the most distinguished in the land and public masters of the Torah but never did a word [relating to mystical lore] escape their lips, and they conducted themselves with [the uninitiated] as with people who were not versed in the [higher] Wisdom, and I beheld their practice and learned my lesson. Furthermore, I have also heard from the regions where you dwell and concerning the men of Burgos that they openly hold forth on these matters, in the marketplaces and in the streets, in confused and hasty discourses, and from their words it is clearly perceptible that their heart has been turned from the All-highest and they cause “cutting off of the shoots,” whereas these things are united as the flame is bound to the coal, for the Lord is unique and has no second [by his side], and what can you count before the One – “before the One,” that is the Great Name, which is united in all of the ten [sefiroth]: but I cannot enter at any greater length, in writing, into what you have asked...

   I cannot perceive any decree of heaven according to which I would now have to leave my place of residence and come to vou. But when R. Asher, the son of my esteemed brother, the learned R. David, may his memory be blessed, comes to you, follow every counsel that he gives you, for I will let you know my will through him. He also knows my position and he saw throughout my life how I conducted myself with regard to my companions.